Concerns have been raised about the suffering of badgers in the forthcoming pilot culls, after official documents were released detailing how welfare impacts will be assessed.
The Government says culling of the protected animal, which can spread TB to cattle, is necessary to help cut spiralling disease rates in dairy and beef herds, but opponents say the policy is not justified by the science and will be inhumane.
The pilots, which are set to kill 5,000 badgers in Somerset and Gloucestershire, aim to ensure culling can be carried out humanely and that sufficient badgers can be killed to have an effect in reducing TB in cattle.
Under the licences issued for the cull, badgers can be trapped in cages and shot in the head or killed through the cheaper method of shooting free-running animals in the chest.
Shooting of free-running badgers will be watched by independent observers to assess duration and intensity of suffering, the document released by the Environment Department (Defra) show. Post-mortem examinations will also be carried out.
The document acknowledges that while some badgers will die very quickly, others may suffer from symptoms such as haemorrhaging and hyperventilation, and if not fatally wounded they could later die from infection or starvation
It also admits that as the number of badgers killed and removed from the environment increases and the opportunity to find and shoot more badgers decreases, "shooters may attempt shots under less than ideal conditions and outside the recommended range".
The behaviour and "vocalisations" of shot badgers will be observed to determine the levels of pain experienced.
But researchers will not approach the animals after they have been shot to assess how long they take to lose consciousness, as "the collection of data must not influence or interfere with the actions of the shooters".
The heavily redacted document also makes reference to monitoring the killing of other wild animals ranging from moose to whales.
Humane Society International UK, which obtained the papers from Defra, said the Government had failed to specify how it would measure suffering of badgers.
HSI/UK's executive director Mark Jones said: "This document provides a shocking insight into the cruel fate that await's England's badgers - a dreadful massacre made all the more horrific because it has no basis whatsoever in science.
"I am also puzzled by comparisons Defra makes to the killing methods of entirely different species. Killing a large whale with a harpoon to the brain, in broad daylight in the middle of the sea, has nothing whatsoever to do with shooting a badger in the chest with a rifle or shotgun in the pitch dark in the middle of a wood.
"The public has not faith in Defra's failed attempts to justify this badger cull, and people will be horrified by the animal suffering. We must kill this cull, not England's badgers."
A spokesman for Defra said: "The design of the study to assess humaneness of the badger culling pilots has been overseen by an independent expert panel, which includes expertise in animal welfare, badger ecology and wildlife population management.
"All marksmen are required to pass a government training course and must adhere to best practice guidance to ensure they can carry out the cull in a humane way.
"The humaneness of the pilots will be monitored through field observations and post mortems and a report will be drawn up by the independent panel at the end of the cull."